Dual Component LLDPE Copolymers with Improved Impact and Tear Resistance, and Methods of Their Preparation

ABSTRACT

Disclosed are ethylene polymer compositions containing a homogeneously-branched first ethylene polymer component and 15-35 wt. % of a homogeneously-branched second ethylene polymer component of higher density than the first ethylene polymer component. The ethylene polymer composition can be characterized by a density from 0.912 to 0.925 g/cm 3 , a ratio of Mw/Mn from 2 to 5, a melt index less than 2 g/10 min, and a CY-a parameter at 190 ° C. from 0.35 to 0.7. These polymer compositions have the excellent dart impact strength and optical properties of a metallocene-catalyzed LLDPE, but with improved machine direction tear resistance, and can be used in blown film and other end-use applications. Further, methods for improving film Elmendorf tear strength also are described.

BACKGROUND OF THE INVENTION

Polyolefins such as high density polyethylene (HDPE) homopolymer andlinear low density polyethylene (LLDPE) copolymer can be produced usingvarious combinations of catalyst systems and polymerization processes.Ziegler-Natta and chromium-based catalyst systems can, for example,produce ethylene polymers having good extrusion processability andpolymer melt strength and bubble stability in blown film applications,typically due to their broad molecular weight distribution (MWD).Further, films produced using Ziegler-Natta catalyst systems have goodtear resistance in both the machine direction (MD) and the transversedirection (TD), but generally suffer from poor impact strength. Incontrast, metallocene-based catalyst systems can, for example, produceethylene polymers having excellent impact strength and opticalproperties, but often lack superior tear resistance, particularly in themachine direction.

In some end-uses, such as blown film applications, it can be beneficialto have the impact resistance and optical properties of ametallocene-catalyzed LLDPE copolymer, but with improved MD tearresistance. Accordingly, it is to these ends that the present inventionis generally directed.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify required oressential features of the claimed subject matter. Nor is this summaryintended to be used to limit the scope of the claimed subject matter.

Aspects of the present invention are directed to ethylene polymercompositions containing (i) a homogeneously-branched first ethylenepolymer component, and (ii) a homogeneously-branched second ethylenepolymer component of higher density than the first ethylene polymercomponent. Generally, the amount of the second ethylene polymercomponent can be in a range from about 15 to about 35 wt. %, or fromabout 20 to about 30 wt. %, based on the total weight of the firstethylene polymer component and the second ethylene polymer component.The ethylene polymer composition can be characterized by a density in arange from about 0.912 to about 0.925 g/cm³, a ratio of Mw/Mn in a rangefrom about 2 to about 5, a melt index less than or equal to about 2 g/10min, and a CY-a parameter at 190° C. in a range from about 0.35 to about0.7.

Additionally or alternatively, the ethylene polymer composition can havean ATREF profile characterized by at least two peaks, with a first peak(a lower temperature peak) at a temperature in a range from about 60 toabout 72° C. (or from about 64 to about 68° C.), and a second peak (ahigher temperature peak) at a temperature in a range from about 92 toabout 104° C. (or from about 95 to about 101° C.). Moreover, thedifference between the temperatures of the two peaks (ΔT) often can fallwithin a range from about 26 to about 39° C. (or from about 29 to about36° C.).

These ethylene polymer compositions can be used to produce variousarticles of manufacture, such as films (e.g., blown films) with abeneficial balance of tear resistance, impact strength, and opticalproperties.

Processes for improving film tear strength and for producing films withdesired tear resistance also are provided in the present invention. Arepresentative process for improving film tear strength of ahomogeneously-branched first ethylene polymer having a density in arange from about 0.90 to about 0.92 g/cm³ can comprise (a) combining thefirst ethylene polymer with from about 15 to about 35 wt. % of ahomogeneously-branched second ethylene polymer having a density in arange from about 0.935 to about 0.972 g/cm³ to form an ethylene polymercomposition, the composition characterized by a melt index of less thanor equal to about 2 g/10 min and a Mw from about 100 to about 200kg/mol, and (b) melt processing the composition through a film die toform a film. The addition of the second ethylene polymer increases a MDElmendorf tear strength of the film.

A representative process for producing a film with a target MD Elmendorftear strength can comprise (a) combining a homogeneously-branched firstethylene polymer having a density in a range from about 0.90 to about0.92 g/cm³ with from about 15 to about 35 wt. % of ahomogeneously-branched second ethylene polymer having a density in arange from about 0.935 to about 0.972 g/cm³ to form an ethylene polymercomposition, the composition characterized by a melt index of less thanor equal to about 2 g/10 min and a Mw from about 100 to about 200kg/mol, and (b) adjusting an amount of the second ethylene polymer inthe composition, and melt processing the composition through a film dieto produce the film with the target MD Elmendorf tear strength. The tearstrength increases as the amount of the second ethylene polymer in thecomposition increases.

Both the foregoing summary and the following detailed descriptionprovide examples and are explanatory only. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Further, features or variations may be provided inaddition to those set forth herein. For example, certain aspects andembodiments may be directed to various feature combinations andsub-combinations described in the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B1-B3.

FIG. 2 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B4-B6.

FIG. 3 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B7-B9.

FIG. 4 presents a plot of the ATREF profiles of the ethylene polymercompositions of Examples B 10-B 14.

FIG. 5 presents a plot of the MD Elmendorf tear strength of blown filmsversus the amount of the high density component (wt. %) in the ethylenepolymer composition.

FIG. 6 presents a plot of the dart impact strength of blown films versusthe amount of the high density component (wt. %) in the ethylene polymercomposition.

FIG. 7 presents a plot of the dart impact strength and the percentageincrease in MD Elmendorf tear strength of blown films versus the amountof the high density component (wt. %) in the ethylene polymercomposition.

FIG. 8 presents a plot of the second heat DSC curve for high densitycomponent HD 3.

FIG. 9 presents a plot of the logarithm of the zero-shear viscosityversus the logarithm of weight-average molecular weight (Mw) for theethylene polymer compositions of Examples B1-B6 and B10-B14.

DEFINITIONS

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2nd Ed (1997), can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Herein, features of the subject matter are described such that, withinparticular aspects, a combination of different features can beenvisioned. For each and every aspect and/or feature disclosed herein,all combinations that do not detrimentally affect the designs,compositions, processes, and/or methods described herein arecontemplated with or without explicit description of the particularcombination. Additionally, unless explicitly recited otherwise, anyaspect and/or feature disclosed herein can be combined to describeinventive features consistent with the present disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsor steps, unless stated otherwise. For example, an ethylene polymercomposition consistent with aspects of the present invention cancomprise; alternatively, can consist essentially of; or alternatively,can consist of; a first ethylene polymer component and a second ethylenepolymer component.

The terms “a,” “an,” “the,” etc., are intended to include pluralalternatives, e.g., at least one, unless otherwise specified.

Generally, groups of elements are indicated using the numbering schemeindicated in the version of the periodic table of elements published inChemical and Engineering News, 63(5), 27, 1985. In some instances, agroup of elements can be indicated using a common name assigned to thegroup; for example, alkali metals for Group 1 elements, alkaline earthmetals for Group 2 elements, transition metals for Group 3-12 elements,and halogens or halides for Group 17 elements.

The term “polymer” is used herein generically to include ethylenehomopolymers, copolymers, terpolymers, and the like, as well as alloysand blends thereof The term “polymer” also includes impact, block,graft, random, and alternating copolymers. A copolymer is derived froman olefin monomer and one olefin comonomer, while a terpolymer isderived from an olefin monomer and two olefin comonomers. Accordingly,“polymer” encompasses copolymers and terpolymers derived from ethyleneand any comonomer(s) disclosed herein. Similarly, the scope of the term“polymerization” includes homopolymerization, copolymerization, andterpolymerization. Therefore, an ethylene polymer would include ethylenehomopolymers, ethylene copolymers (e.g., ethylene/α-olefin copolymers),ethylene terpolymers, and the like, as well as blends or mixturesthereof. Thus, an ethylene polymer encompasses polymers often referredto in the art as LLDPE (linear low density polyethylene) and HDPE (highdensity polyethylene). As an example, an ethylene copolymer can bederived from ethylene and a comonomer, such as 1-butene, 1-hexene, or1-octene. If the monomer and comonomer were ethylene and 1-hexene,respectively, the resulting polymer could be categorized an asethylene/1-hexene copolymer. The term “polymer” also includes allpossible geometrical configurations, unless stated otherwise, and suchconfigurations can include isotactic, syndiotactic, and randomsymmetries. Moreover, unless stated otherwise, the term “polymer” alsois meant to include all molecular weight polymers.

The terms “catalyst composition,” “catalyst mixture,” “catalyst system,”and the like, do not depend upon the actual product or compositionresulting from the contact or reaction of the initial components of thedisclosed or claimed catalyst composition/mixture/system, the nature ofthe active catalytic site, or the fate of the co-catalyst, themetallocene compound, or the activator (e.g., activator-support), aftercombining these components. Therefore, the terms “catalyst composition,”“catalyst mixture,” “catalyst system,” and the like, encompass theinitial starting components of the composition, as well as whateverproduct(s) may result from contacting these initial starting components,and this is inclusive of both heterogeneous and homogenous catalystsystems or compositions. The terms “catalyst composition,” “catalystmixture,” “catalyst system,” and the like, can be used interchangeablythroughout this disclosure.

Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of theinvention, the typical methods, devices, and materials are hereindescribed.

All publications and patents mentioned herein are incorporated herein byreference for the purpose of describing and disclosing, for example, theconstructs and methodologies that are described in the publications,which might be used in connection with the presently describedinvention.

Several types of ranges are disclosed in the present invention. When arange of any type is disclosed or claimed, the intent is to disclose orclaim individually each possible number that such a range couldreasonably encompass, including end points of the range as well as anysub-ranges and combinations of sub-ranges encompassed therein. Forexample, by a disclosure that the ratio of Mw/Mn can be in a range fromabout 2 to about 5, the intent is to recite that the ratio of Mw/Mn canbe any ratio in the range and, for example, can be equal to about 2,about 2.5, about 3, about 3.5, about 4, about 4.5, or about 5.Additionally, the ratio of Mw/Mn can be within any range from about 2 toabout 5 (for example, from about 2.2 to about 4), and this also includesany combination of ranges between about 2 and about 5. Further, in allinstances, where “about” a particular value is disclosed, then thatvalue itself is disclosed. Thus, the disclosure that the ratio of Mw/Mncan be from about 2 to about 5 also discloses a ratio of Mw/Mn from 2 to5 (for example, from 2.2 to 4), and this also includes any combinationof ranges between 2 and 5. Likewise, all other ranges disclosed hereinshould be interpreted in a manner similar to this example.

The term “about” means that amounts, sizes, formulations, parameters,and other quantities and characteristics are not and need not be exact,but may be approximate and/or larger or smaller, as desired, reflectingtolerances, conversion factors, rounding off, measurement errors, andthe like, and other factors known to those of skill in the art. Ingeneral, an amount, size, formulation, parameter or other quantity orcharacteristic is “about” or “approximate” whether or not expresslystated to be such. The term “about” also encompasses amounts that differdue to different equilibrium conditions for a composition resulting froma particular initial mixture. Whether or not modified by the term“about,” the claims include equivalents to the quantities. The term“about” can mean within 10% of the reported numerical value, preferablywithin 5% of the reported numerical value.

As used herein, “MD” refers to machine direction, and “CD” refers tocross direction. The cross direction also can be referred to herein asthe transverse direction (TD).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed generally to ethylene polymercompositions containing a lower density component and a higher densitycomponent. Articles produced from these ethylene-based polymercompositions, such as blown films, can have excellent dart impact, tearstrength (e.g., MD Elmendorf tear strength), and optical properties,despite the presence of the higher density component in the polymercomposition. Further, methods for improving and for controlling (oradjusting) the tear strength of a film product also are disclosedherein.

Ethylene Polymer Compositions

Generally, the ethylene polymer compositions disclosed herein contain(i) a homogeneously-branched first ethylene polymer component, and (ii)a homogeneously-branched second ethylene polymer component of higherdensity than the first ethylene polymer component. The first ethylenepolymer component and the second ethylene polymer component areethylene-based polymers, or ethylene polymers, encompassing homopolymersof ethylene as well as copolymers, terpolymers, etc., of ethylene and atleast one olefin comonomer. Comonomers that can be copolymerized withethylene often can have from 3 to 20 carbon atoms in their molecularchain. For example, typical comonomers can include, but are not limitedto, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, andthe like, or combinations thereof. In an aspect, the olefin comonomercan comprise a C₃-C18 olefin; alternatively, the olefin comonomer cancomprise a C₃-C₁₀ olefin; alternatively, the olefin comonomer cancomprise a C₄-Cm olefin; alternatively, the olefin comonomer cancomprise a C₃-C₁₀ α-olefin; alternatively, the olefin comonomer cancomprise a C₄-C₁₀ α-olefin; alternatively, the olefin comonomer cancomprise 1-butene, 1-hexene, 1-octene, or any combination thereof; oralternatively, the comonomer can comprise 1-hexene. Typically, theamount of the comonomer, based on the total weight of monomer (ethylene)and comonomer, can be in a range from about 0.01 to about 20 wt. %, fromabout 0.1 to about 10 wt. %, from about 0.5 to about 15 wt. %, fromabout 0.5 to about 8 wt. %, or from about 1 to about 15 wt. %.

In one aspect, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component of thisinvention, independently, can comprise an ethylene/α-olefin copolymerand/or an ethylene homopolymer. Thus, the ethylene polymer composition,in some aspects, can comprise an ethylene/α-olefin copolymer and anethylene homopolymer.

In another aspect, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component,independently, can comprise an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, an ethylene/1-octene copolymer, an ethylenehomopolymer, or any combination thereof; alternatively, anethylene/1-butene copolymer, an ethylene/1-hexene copolymer, anethylene/1-octene copolymer, or any combination thereof; oralternatively, an ethylene/1-hexene copolymer. Consistent with aspectsof the present invention, the ethylene polymer composition, the firstethylene polymer component, and the second ethylene polymer component,independently, can have any of the polymer properties listed below andin any combination, unless indicated otherwise.

The ethylene polymer composition can be characterized by a density in arange from about 0.912 to about 0.925 g/cm³. For example, the ethylenepolymer composition can have a density in a range from about 0.912 toabout 0.922 g/cm³; alternatively, from about 0.912 to about 0.92 g/cm³;or alternatively, from about 0.915 to about 0.925 g/cm³.

The first ethylene polymer component is a lower density component, i.e.,the first ethylene polymer component has a lower density than that ofthe second ethylene polymer component. In one aspect, the first ethylenepolymer component can have a density in a range from about 0.89 to about0.92 g/cm³, while in another aspect, the density can be in a range fromabout 0.90 to about 0.92 g/cm³, and in yet another aspect, from about0.905 to about 0.918 g/cm³, and in still another aspect, from about 0.91to about 0.918 g/cm³.

The second ethylene polymer component is a higher density component,i.e., the second ethylene polymer component has a higher density thanthat of the first ethylene polymer component. In one aspect, forinstance, the second ethylene polymer component can have a density in arange from about 0.935 to about 0.972 g/cm³, while in another aspect,the density can be in a range from about 0.94 to about 0.97 g/cm³, andin yet another aspect, from about 0.94 to about 0.96 g/cm³, and in stillanother aspect, from about 0.945 to about 0.965 g/cm³.

While not being limited thereto, the amount of the second ethylenepolymer component often can be in a range from about 15 to about 35 wt.%, from about 15 to about 30 wt. %, from about 15 to about 28 wt. %, orfrom about 15 to about 25 wt. %, based on the total weight of the firstethylene polymer component and the second ethylene polymer component. Inother aspects, the amount of the second ethylene polymer component canbe in a range from about 20 to about 35 wt. %, from about 20 to about 30wt. %, from about 18 to about 32 wt. %, or from about 18 to about 28 wt.%, based on the total weight of the first ethylene polymer component andthe second ethylene polymer component.

The respective melt index (MI) of the ethylene polymer composition andthe first ethylene polymer component, independently, can be less than orequal to about 2 g/10 min, less than or equal to about 1.5 g/10 min, orless than or equal to about 1.3 g/10 min. Typical ranges for the MI ofthe ethylene polymer composition and/or the first ethylene polymercomponent can include, but are not limited to, from about 0.3 to about 2g/10 min, from about 0.3 to about 1.5 g/10 min, from about 0.5 to about2 g/10 min, from about 0.5 to about 1.8 g/10 min, or from about 0.5 toabout 1.5 g/10 min.

The melt index of the second ethylene polymer component generally is notnecessarily limited to the same ranges as that of the first ethylenepolymer component. For instance, the second ethylene polymer componentcan have a MI of less than or equal to about 50 g/10 min, less than orequal to about 10 g/10 min, or less than or equal to about 5 g/10 min,with representative non-limiting ranges including from about 0.3 toabout 2 g/10 min, from about 0.5 to about 40 g/10 min, from about 0.5 toabout 8 g/10 min, from about 0.4 to about 4 g/10 min, or from about 10to about 25 g/10 min.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of HLMI/MI (high load melt index/melt index; melt index not equalto zero) in a range from about 10 to about 35, from about 12 to about30, from about 12 to about 25, from about 12 to about 20, from about 15to about 35, from about 15 to about 30, from about 15 to about 25, orfrom about 15 to about 22, and the like.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of Mw/Mn, or polydispersity index, in a range from about 2 toabout 5, from about 2 to about 4, from about 2 to about 3.5, or fromabout 2 to about 3, in some aspects of this invention, and from about2.2 to about 5, from about 2.2 to about 4, from about 2.2 to about 3.5,from about 2.2 to about 3.2, or from about 2.2 to about 3, in otheraspects of this invention.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aratio of Mz/Mw in a range from about 1.7 to about 3, or from about 1.7to about 2.5, in some aspects of this invention, and from about 1.7 toabout 2.3, from about 1.7 to about 2.2, or from about 1.7 to about 2, inother aspects of this invention.

The respective weight-average molecular weight (Mw) of the ethylenepolymer composition and the first ethylene polymer component,independently, can be from about 100 to about 200 kg/mol, or from about100 to about 150 kg/mol. Other suitable ranges include from about 110 toabout 200 kg/mol, from about 110 to about 180 kg/mol, or from about 110to about 160 kg/mol.

The Mw of the second ethylene polymer component generally is notnecessarily limited to the same ranges as that of the first ethylenepolymer component. For instance, the second ethylene polymer componentcan have a Mw from about 85 to about 200 kg/mol, from about 85 to about160 kg/mol, or from about 100 to about 200 kg/mol, in some aspects ofthis invention, and from about 40 to about 180 kg/mol, or from about 40to about 150 kg/mol, in other aspects of this invention.

Consistent with one aspect of this invention, the Mw of the firstethylene polymer component can be greater than the Mw of the secondethylene polymer component, which can result in improved film opticalproperties and film MD tear resistance as compared to circumstances inwhich the molecular weights are reversed. In this aspect, the ratio ofthe Mw of the first ethylene polymer component to the Mw of the secondethylene polymer component typically can fall within a range from about1.1:1 to about 5:1, from about 1.1:1 to about 3:1, from about 1.1:1 toabout 1.8:1, from about 1.2:1 to about 4:1, or from about 1.2:1 to about2.5:1.

Consistent with another aspect of this invention, the Mw of the firstethylene polymer component can be less than the Mw of the secondethylene polymer component. In this aspect, the ratio of the Mw of thefirst ethylene polymer component to the Mw of the second ethylenepolymer component typically can fall within a range from about 0.5:1 toabout 0.9:1, from about 0.6:1 to about 0.9:1, from about 0.65:1 to about0.9:1, or from about 0.7:1 to about 0.9:1.

Consistent with yet another aspect of this invention, the Mw of thefirst ethylene polymer component can be substantially the same as thatof the Mw of the second ethylene polymer component (of similar molecularsize). In this aspect, the ratio of the Mw of the first ethylene polymercomponent to the Mw of the second ethylene polymer component typicallycan fall within a range from about 0.75:1 to about 1.25:1, from about0.8:1 to about 1.2:1, from about 0.9:1 to about 1.1:1, or from about0.8:1 to about 1.1:1.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aunimodal molecular weight distribution (as determined using gelpermeation chromatography (GPC) or other suitable analytical technique).In a unimodal molecular weight distribution, there is a singleidentifiable peak. Often, each of the ethylene polymer composition, thefirst ethylene polymer component, and the second ethylene polymercomponent, has a unimodal molecular weight distribution.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component can have aCY-a parameter (at 190° C.) in a range from about 0.35 to about 0.7;alternatively, from about 0.35 to about 0.6; alternatively, from about0.4 to about 0.7; alternatively, from about 0.4 to about 0.65;alternatively, from about 0.4 to about 0.55; alternatively, from about0.45 to about 0.7; or alternatively, from about 0.45 to about 0.65.

The respective zero-shear viscosity (at 190° C.) of the ethylene polymercomposition and the first ethylene polymer component, independently, canbe from about 2,500 to about 25,000 Pa-sec, or from about 3,000 to about25,000 Pa-sec. Other suitable ranges include from about 2,500 to about20,000 Pa-sec, from about 3,000 to about 20,000 Pa-sec, or from about4,000 to about 15,000 Pa-sec.

The zero-shear viscosity (at 190° C.) of the second ethylene polymercomponent generally is not necessarily limited to the same ranges asthat of the first ethylene polymer component. For instance, the secondethylene polymer component can have a zero-shear viscosity from about2,500 to about 25,000 Pa-sec, or from about 5,000 to about 70,000Pa-sec, in some aspects of this invention, and from about 150 to about2,500 Pa-sec, or from about 500 to about 5,000 Pa-sec, in other aspectsof this invention.

The zero-shear viscosity and the CY-a parameter are determined fromviscosity data measured at 190° C. and using the Carreau-Yasuda (CY)empirical model as described herein.

The ethylene polymer composition, the first ethylene polymer component,and the second ethylene polymer component typically have low levels oflong chain branches (LCB). For instance, the ethylene polymercomposition, the first ethylene polymer component, and the secondethylene polymer component, independently, can have less than 10 longchain branches (LCB), less than 8 LCB, less than 5 LCB, or less than 3LCB, per million total carbon atoms.

Independently, the ethylene polymer composition, the first ethylenepolymer component, and the second ethylene polymer component, can have areverse short chain branching distribution (reverse SCBD; increasingcomonomer distribution) or a flat short chain branching distribution(flat SCBD; uniform comonomer distribution), and these distributions canbe indicative of homogeneously-branched polymer components. As one ofskill in the art would readily recognize, the profile of the SCBD is notapplicable when the second ethylene polymer component is an ethylenehomopolymer.

A reverse SCBD can be characterized by the number of short chainbranches (SCB) per 1000 total carbon atoms of the ethylene polymer at Mwthat is greater than at Mn, and/or the number of SCB per 1000 totalcarbon atoms of the ethylene polymer at Mz that is greater than at Mw,and/or the number of SCB per 1000 total carbon atoms of the ethylenepolymer at Mz that is greater than at Mn.

A flat SCBD can be characterized by a slope of a plot of the number ofshort chain branches (SCB) per 1000 total carbon atoms versus thelogarithm of molecular weight of the ethylene polymer (determined vialinear regression over the range from D15 to D85) that is in a rangefrom about -0.6 to about 0.6, and/or a percentage of data pointsdeviating from the average short chain branch content by greater than0.5 short chain branches per 1000 total carbon atoms (determined overthe range from D15 to D85) that is less than or equal to about 20%,and/or a percentage of data points deviating from the average shortchain branch content by greater than 1 short chain branch per 1000 totalcarbon atoms (determined over the range from D15 to D85) that is lessthan or equal to about 10%. Polymers having a flat or uniform SCBD aredisclosed, for example, in U.S. Pat. Nos. 9,217,049 and 9,574,031, whichare incorporated herein by reference in their entirety.

In accordance with certain aspects of this invention, the ethylenepolymer compositions described herein can have a unique ATREF profile.For instance, the ethylene polymer composition can be characterized byan ATREF curve containing at least two peaks (in the 60-104° C. range),with a first peak (a lower temperature peak) at a temperature in a rangefrom about 60 to about 72° C., such as from about 62 to about 70° C.,from about 63 to about 69° C., or from about 64 to about 68° C.Additionally or alternatively, the ethylene polymer composition can becharacterized by an ATREF curve containing at least two peaks (in the60-104° C. range), with a second peak (a higher temperature peak) at atemperature in a range from about 92 to about 104° C., such as fromabout 93 to about 103° C., from about 94 to about 102° C., or from about95 to about 101° C.

Additionally or alternatively, the ethylene polymer composition can becharacterized by an ATREF curve containing at least two peaks in thetemperature range from about 60 to about 104° C., and the differencebetween the temperatures of the two peaks (ΔT) can be in a range fromabout 26 to about 39° C., from about 28 to about 37° C., or from about29 to about 36° C. In these and other aspects, the peak ATREFtemperature (temperature of the highest peak on the ATREF curve) can beeither the lower temperature peak or the higher temperature peak. Infurther aspects, in addition to the aforementioned lower and highertemperature peaks, there are no other significant peaks on the ATREFcurve above a dW/dT of 1 in height (plot of dW/dT vs. T; normalized toan area equal to 1).

Consistent with aspects of this invention, the first ethylene polymercomponent and the second ethylene polymer component, independently, canbe produced using a zirconium-based metallocene catalyst system. Forexample, the catalyst system can comprise a zirconium-containingmetallocene compound (bridged or unbridged), an activator, and anoptional co-catalyst. In such aspects, the first ethylene polymercomponent and the second ethylene polymer component are not producedusing a hafnium-based and/or a titanium-based catalyst system.

Further, and independently, the ethylene polymer composition, the firstethylene polymer component, and the second ethylene polymer component,can contain no measurable amount of hafnium or titanium (catalystresidue), i.e., less than 0.1 ppm by weight. In some aspects, theethylene polymer composition, the first ethylene polymer component, andthe second ethylene polymer component, independently, can contain lessthan 0.08 ppm, less than 0.05 ppm, or less than 0.03 ppm, of eitherhafnium or titanium.

In an aspect, the ethylene polymer composition described herein can be areactor product (e.g., a single reactor product) containing the firstethylene polymer component and the second ethylene polymer component,for example, not a post-reactor blend of the first ethylene polymercomponent and the second ethylene polymer component. However, in anotheraspect of this invention, the ethylene polymer composition describedherein can be blend or mixture (e.g., a post-reactor blend) containingthe first ethylene polymer component and the second ethylene polymercomponent. The ethylene polymer composition can be in any suitable form,such as powder, fluff, or pellets.

Typically, a large majority or substantially all of the ethylene polymercomposition is the first ethylene polymer component and the secondethylene polymer component. In an aspect, the total amount of the firstethylene polymer component and the second ethylene polymer component inthe ethylene polymer composition can be at least about 75 wt. %, atleast about 85 wt. %, at least about 90 wt. %, at least about 95 wt. %,at least about 98 wt. %, or at least about 99 wt. %, and this is basedon the total weight of the composition. As one of skill in the art wouldreadily recognize, the ethylene polymer composition can further includeone or more suitable additives, such as an antioxidant, an acidscavenger, an antiblock additive, a slip additive, a colorant, a filler,a polymer processing aid, a UV additive, and the like, as well ascombinations thereof. Moreover, as one of skill in the would readilyrecognize, the ethylene polymer composition can further contain otherpolymer components—in addition to the first ethylene polymer componentand the second ethylene polymer component—and illustrative andnon-limiting polymer components can include low density polyethylene(LDPE), ethylene vinyl acetate (EVA), and the like. In particularaspects of this invention, the only polymer components of the ethylenepolymer composition are the first ethylene polymer component and thesecond ethylene polymer component.

Articles and Products

Articles of manufacture can be produced from, and/or can comprise, theethylene polymer compositions of this invention and, accordingly, areencompassed herein. For example, articles that can comprise ethylenepolymer compositions of this invention can include, but are not limitedto, an agricultural film, an automobile part, a bottle, a container forchemicals, a drum, a fiber or fabric, a food packaging film orcontainer, a food service article, a fuel tank, a geomembrane, ahousehold container, a liner, a molded product, a medical device ormaterial, an outdoor storage product, outdoor play equipment, a pipe, asheet or tape, a toy, or a traffic barrier, and the like. Variousprocesses can be employed to form these articles. Non-limiting examplesof these processes include injection molding, blow molding, rotationalmolding, film extrusion, sheet extrusion, profile extrusion,thermoforming, and the like. Additionally, additives and modifiers oftenare added to these polymer compositions in order to provide beneficialpolymer processing or end-use product attributes. Such processes andmaterials are described in Modern Plastics Encyclopedia, Mid-November1995 Issue, Vol. 72, No. 12; and Film Extrusion Manual—Process,Materials, Properties, TAPPI Press, 1992; the disclosures of which areincorporated herein by reference in their entirety. In some aspects ofthis invention, the article of manufacture can comprise (or can beproduced from) any of ethylene polymer compositions described herein,and the article of manufacture can be or can comprise a film.

In some aspects, the article produced from and/or comprising an ethylenepolymer composition of this invention is a film product. For instance,the film can be a blown film or a cast film that is produced from and/orcomprises any of the ethylene polymer compositions disclosed herein.Such films also can contain one or more additives, non-limiting examplesof which can include an antioxidant, an acid scavenger, an antiblockadditive, a slip additive, a colorant, a filler, a processing aid, a UVinhibitor, and the like, as well as combinations thereof.

Also contemplated herein is a method for making a film (e.g., a blownfilm, a cast film, etc.) comprising any ethylene polymer compositiondisclosed herein. For instance, the method can comprise melt processingthe ethylene polymer composition through a die to form the film.Suitably, the die can be configured based on the film to be produced,for example, an annular blown film die to produce a blown film, a slotor cast film die to produce a cast film, and so forth. Moreover, anysuitable means of melt processing can be employed, although extrusiontypically can be utilized. As above, additives can be combined with thepolymer composition in the melt processing step (extrusion step), suchas antioxidants, acid scavengers, antiblock additives, slip additives,colorants, fillers, processing aids, UV inhibitors, and the like, aswell as combinations thereof.

Films disclosed herein, whether cast or blown, can be any thickness thatis suitable for the particular end-use application, and often, theaverage film thickness can be in a range from about 0.25 to about 25mils, or from about 0.4 to about 20 mils. For certain film applications,typical average thicknesses can be in a range from about 0.5 to about 8mils, from about 0.8 to about 5 mils, from about 0.7 to about 2 mils, orfrom about 0.7 to about 1.5 mils.

In an aspect and unexpectedly, the films disclosed herein (e.g., blownfilms) can have excellent impact strength, tear resistance, and opticalproperties, despite the presence of the second ethylene polymercomponent (the higher density component). For instance, a filmconsistent with aspects of this invention can have a dart impactstrength greater than or equal to about 250 g/mil. In some aspects, thefilm can have a dart impact greater than or equal to about 400 g/mil,greater than or equal to about 500 g/mil, greater than or equal to about700 g/mil, greater than or equal to about 900 g/mil, greater than orequal to about 1000 g/mil, or greater than or equal to about 1400 g/mil,and often can range up to about 1500-2000 g/mil or more. For many filmapplications, the upper limit on dart impact is not determined, so longas the dart impact exceeds a particular minimal value or threshold.

The film also can be characterized by its Spencer impact strength.Spencer impact strengths often can be in a range from about 0.3 to about2 J/mil, or from about 0.4 to about 1.5 J/mil, but are not limitedthereto.

In another aspect, blown or cast films described herein can becharacterized by the MD (or TD) Elmendorf tear strength. Suitable rangesfor the MD tear strength can include, but are not limited to, from about100 to about 500 g/mil, from about 150 to about 500 g/mil, from about100 to about 450 g/mil, from about 125 to about 425 g/mil, from about150 to about 450 g/mil, from about 200 to about 450 g/mil, or from about225 to about 475 g/mil. Suitable ranges for the TD tear strength caninclude, but are not limited to, from about 200 to about 800 g/mil, fromabout 250 to about 800 g/mil, from about 300 to about 800 g/mil, fromabout 400 to about 800 g/mil, from about 250 to about 700 g/mil, or fromabout 300 to about 600 g/mil.

Advantageously, and unexpectedly, the film products of this inventionhave a good balance of tear properties, as generally quantified by theratio of MD Elmendorf tear strength to TD Elmendorf tear strength(MD:TD). Often, this MD:TD ratio falls in a range from about 0.25:1 toabout 0.8:1, from about 0.25:1 to about 0.7:1, from about 0.25:1 toabout 0.6:1, from about 0.3:1 to about 0.8:1, from about 0.3:1 to about0.7:1, or from about 0.3:1 to about 0.6:1.

In an aspect, film products of this invention (e.g., nominal 1-milfilms) also can be characterized by very good optical properties, suchas low haze and high clarity, e.g., particularly in the absence of anyadditives that might impact such measurements, such as slip andantiblock additives. Representative blown and cast films describedherein can have a film haze of less than or equal to about 12%, lessthan or equal to about 10%, in a range from about 2 to about 10%, or ina range from about 2 to about 8%, and often the film haze can range downto 1-3%. Similarly, the clarity of the films contemplated herein oftencan be at least about 70%, at least about 75%, at least about 80%, or atleast about 85%.

An illustrative and non-limiting example of a film product (producedfrom or comprising the ethylene polymer composition) consistent with thepresent invention can have a MD Elmendorf tear strength in a range fromabout 100 to about 500 g/mil (or from about 150 to about 450 g/mil), anda ratio of MD Elmendorf tear strength to TD Elmendorf tear strength(MD:TD) in a range from about 0.3:1 to about 0.8:1 (or from about 0.3:1to about 0.7:1). This illustrative and non-limiting example of a filmproduct consistent with the present invention also can have any of thepolymer and film properties and features listed herein and in anycombination, unless indicated otherwise.

Processes for Improving or Controlling Tear Resistance

The present invention also encompasses processes for improving film tearstrength. One such process for improving the film tear strength of ahomogeneously-branched first ethylene polymer—having a density in arange from about 0.90 to about 0.92 g/cm³—can comprise (a) combining thefirst ethylene polymer with from about 15 to about 35 wt. % of ahomogeneously-branched second ethylene polymer having a density in arange from about 0.935 to about 0.972 g/cm³ to form an ethylene polymercomposition, and (b) melt processing the ethylene polymer compositionthrough a film die to form a film. The ethylene polymer composition canbe characterized by a melt index of less than or equal to about 2 g/10min and a Mw from about 100 to about 200 kg/mol. Significantly, theaddition of the second ethylene polymer increases the MD Elmendorf tearstrength of the film.

Another aspect of the present invention is directed to a process forproducing a film with a target MD Elmendorf tear strength. A process inaccordance with this aspect can comprise (a) combining ahomogeneously-branched first ethylene polymer having a density in arange from about 0.90 to about 0.92 g/cm³ with from about 15 to about 35wt. % of a homogeneously-branched second ethylene polymer having adensity in a range from about 0.935 to about 0.972 g/cm³ to form anethylene polymer composition, and (b) adjusting an amount of the secondethylene polymer in the composition, and melt processing the compositionthrough a film die to produce the film with the target MD Elmendorf tearstrength. The ethylene polymer composition can be characterized by amelt index of less than or equal to about 2 g/10 min and a Mw from about100 to about 200 kg/mol. Significantly, the film tear strength increasesas the amount of the second ethylene polymer in the compositionincreases.

Generally, the features of these processes (for example, thecharacteristics of the first ethylene polymer, the characteristics ofthe second ethylene polymer, the characteristics of the ethylene polymercomposition, the amount of the second ethylene polymer, and the MDElmendorf tear strength, among others) are independently describedherein and these features can be combined in any combination to furtherdescribe the disclosed processes. Moreover, other steps can be conductedbefore, during, and/or after any of the steps listed in the disclosedprocesses, unless stated otherwise.

Any of the properties of the first ethylene polymer, the second ethylenepolymer, and the ethylene polymer composition in these processes can bethe same as those described herein in relation to ethylene polymercompositions, components, and film products formed therefrom. Forinstance, the ethylene polymer composition can have any density fromabout 0.912 to about 0.925 g/cm³, any melt index less than or equal toabout 2 g/10 min, any HLMI/MI from about 10 to about 35, any Mw/Mn fromabout 2 to about 5, any Mz/Mw from about 1.7 to about 3, any Mw fromabout 100 to about 200 kg/mol, any CY-a parameter from about 0.35 toabout 0.7, any zero-shear viscosity from about 2,500 to about 25,000Pa-sec, any branching distribution disclosed herein, any LCB contentdisclosed herein, and any ATREF features disclosed herein (e.g., a lowertemperature peak from about 60 to about 72° C. and a higher temperaturepeak from about 92 to about 104° C.), and in any combination.

Similarly, the first ethylene polymer can have any density from about0.90 to about 0.92 g/cm³, any melt index less than or equal to about 2g/10 min, any HLMI/MI from about 10 to about 35, any Mw/Mn from about 2to about 5, any Mz/Mw from about 1.7 to about 3, any Mw from about 100to about 200 kg/mol, any CY-a parameter from about 0.35 to about 0.7,any zero-shear viscosity from about 2,500 to about 25,000 Pa-sec, anybranching distribution disclosed herein, and any LCB content disclosedherein, and in any combination.

Likewise, any amount the second ethylene polymer from about 15 to about35 wt. % can be utilized, and the second ethylene polymer can have anydensity from about 0.935 to about 0.972 g/cm³, any melt index less thanor equal to about 50 g/10 min, any HLMI/MI from about 10 to about 35,any Mw/Mn from about 2 to about 5, any Mz/Mw from about 1.7 to about 3,any Mw from about 40 to about 200 kg/mol, any CY-a parameter from about0.35 to about 0.7, any zero-shear viscosity from about 150 to about70,000 Pa-sec, any branching distribution disclosed herein, and any LCBcontent disclosed herein, and in any combination.

Additionally, the total amount of the first ethylene polymer and thesecond ethylene polymer in the ethylene polymer composition can at leastabout 75 wt. % (e.g., at least about 95 wt. %), based on the totalweight of the ethylene polymer composition, and any suitable additivecan be present in the composition, non-limiting examples of which caninclude an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,and the like, as well as combinations thereof.

In like manner, the films produced by these processes can have any filmattributes disclosed herein. The film thickness can be any averagethickness from about 0.4 to about 20 mils, and the film can be a blownfilm or a cast film. The film can be characterized by any haze less thanor equal to about 12%, any clarity of at least about 70%, any dartimpact strength of at least about 250 g/mil, any Spencer impact strengthfrom about 0.3 to about 2 J/mil, any MD Elmendorf tear strength fromabout 100 to about 500 g/mil, any TD Elmendorf tear strength from about200 to about 800 g/mil, and any ratio of MD Elmendorf tear strength toTD Elmendorf tear strength (MD:TD) from about 0.25:1 to about 0.8:1, andin any combination.

As it pertains to these processes for improving film tear strength andfor producing a film with a target MD Elmendorf tear strength, it wasunexpectedly found that the addition of ˜15-35 wt. % of the (higherdensity) second ethylene polymer increases the MD Elmendorf tearstrength of the film. Beneficially, the film Elmendorf tear strengthincreases as the amount of the second ethylene polymer in the ethylenepolymer composition increases.

Also unexpectedly, in certain aspects of this invention, the addition ofthe second ethylene polymer does not significantly affect the dartimpact strength of the film. For instance, the improvement in MDElmendorf tear strength can be achieved concurrently with no substantialchange in the dart impact strength of the film, i.e., the change in dartimpact is less than about 20%. As an example, if the dart impactstrength of a film produced using only the first ethylene polymer is1400 g/mil, and the dart impact strength of a film produced using 20 wt.% of the second ethylene polymer (with 80 wt. % of the first ethylenepolymer) is 1300 g/mil, then the change in dart impact is approximately7%.

In further aspects of this invention, the addition of the secondethylene polymer also does not significantly affect the opticalproperties of the film. For instance, the improvement in MD Elmendorftear strength can be achieved concurrently with no substantial change inthe haze of the film, i.e., the change in haze is within +/−3 (percenthaze units). As an example, if the haze of a film produced using onlythe first ethylene polymer is 4.5%, and the haze of a film producedusing 22 wt. % of the second ethylene polymer (with 78 wt. % of thefirst ethylene polymer) is 6.3%, then the change in haze is 1.8%.

These combined attributes of excellent impact resistance and opticalproperties, but with improved tear resistance, as quantified by the MDElmendorf tear strength, of the film products described herein areparticularly beneficial and unexpected based solely on the properties ofthe individual components. As would be readily recognized, theproperties of blown and cast films, with significant differences inpolymer drawdown/orientation and polymer cooling/quenching, cannot bereadily predicted or ascertained from thick part or molded properties inwhich orientation and quenching effects are not comparable.

EXAMPLES

The invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, maysuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims.

Melt index (MI, g/10 min) was determined in accordance with ASTM D1238at 190° C. with a 2,160 gram weight, and high load melt index (HLMI,g/10 min) was determined in accordance with ASTM D1238 at 190° C. with a21,600 gram weight. Density was determined in grams per cubic centimeter(g/cm³) on a compression molded sample, cooled at 15° C. per hour, andconditioned for 40 hours at room temperature in accordance with ASTMD1505 and ASTM D4703.

Molecular weights and molecular weight distributions were obtained usinga PL-GPC 220 (Polymer Labs, an Agilent Company) system equipped with aIR4 detector (Polymer Char, Spain) and three Styragel HMW-6E GPC columns(Waters, MA) running at 145° C. The flow rate of the mobile phase1,2,4-trichlorobenzene (TCB) containing 0.5 g/L2,6-di-t-butyl-4-methylphenol (BHT) was set at 1 mL/min, and polymersolution concentrations were in the range of 1.0-1.5 mg/mL, depending onthe molecular weight. Sample preparation was conducted at 150° C. fornominally 4 hr with occasional and gentle agitation, before thesolutions were transferred to sample vials for injection. An injectionvolume of about 200 μL was used. The integral calibration method wasused to deduce molecular weights and molecular weight distributionsusing a Chevron Phillips Chemical Company's HDPE polyethylene resin,MARLEX® BHB5003, as the standard. The integral table of the standard waspre-determined in a separate experiment with SEC-MALS. Mn is thenumber-average molecular weight, Mw is the weight-average molecularweight, Mz is the z-average molecular weight, and Mp is the peakmolecular weight (location, in molecular weight, of the highest point ofthe molecular weight distribution curve).

Melt rheological characterizations were performed as follows.Small-strain (less than 10%) oscillatory shear measurements wereperformed on an Anton Paar MCR rheometer using parallel-plate geometry.All rheological tests were performed at 190° C. The complex viscosity|η*| versus frequency (ω) data were then curve fitted using the modifiedthree parameter Carreau-Yasuda (CY) empirical model to obtain thezero-shear viscosity—η₀, characteristic viscous relaxation time—τ_(η),and the breadth parameter—α(CY-a parameter). The simplifiedCarreau-Yasuda (CY) empirical model is as follows.

${\left| {\eta*(\omega)} \right| = \frac{\eta_{0}}{\left\lbrack {1 + \left( {\tau_{\eta}\omega} \right)^{a}} \right\rbrack^{{({1 - n})}/a}}},$

wherein: |η*(ω)|=magnitude of complex shear viscosity;

-   -   η₀=zero-shear viscosity;    -   τ_(n)=viscous relaxation time (Tau(η));    -   a=“breadth” parameter (CY-a parameter);    -   n=fixes the final power law slope, fixed at 2/11; and    -   ω=angular frequency of oscillatory shearing deformation.

Details of the significance and interpretation of the CY model andderived parameters can be found in: C. A. Hieber and H. H. Chiang,Rheol. Acta, 28, 321 (1989); C. A. Hieber and H. H. Chiang, Polym. Eng.Sci., 32, 931 (1992); and R. B. Bird, R. C. Armstrong and O. Hasseger,Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, 2nd Edition,John Wiley & Sons (1987); each of which is incorporated herein byreference in its entirety.

The ATREF procedure was as follows. Forty mg of the polymer sample and20 mL of 1,2,4-trichlorobenzene (TCB) were sequentially charged into avessel on a PolyChar TREF 200 +instrument. After dissolving the polymer,an aliquot (500 microliters) of the polymer solution was loaded on thecolumn (stainless steel shots) at 150° C. and cooled at 0.5° C./min to25° C. Then, the elution was begun with a 0.5 mL/min TCB flow rate andheating at 1° C./min up to 120° C., and analyzing with an IR detector.The peak ATREF temperature is the location, in temperature, of thehighest point of the ATREF curve.

Short chain branch content and short chain branching distribution (SCBD)across the molecular weight distribution can be determined via anIR5-detected GPC system (IR5-GPC), wherein the GPC system is a PL220GPC/SEC system (Polymer Labs, an Agilent company) equipped with threeStyragel HMW-6E columns (Waters, Mass.) for polymer separation. Athermoelectric-cooled IRS MCT detector (IRS) (Polymer Char, Spain) isconnected to the GPC columns via a hot-transfer line. Chromatographicdata is obtained from two output ports of the IRS detector. First, theanalog signal goes from the analog output port to a digitizer beforeconnecting to Computer “A” for molecular weight determinations via theCirrus software (Polymer Labs, now an Agilent Company) and the integralcalibration method using a HDPE Marlex™ BHB5003 resin (Chevron PhillipsChemical) as the molecular weight standard. The digital signals, on theother hand, go via a USB cable directly to Computer “B” where they arecollected by a LabView data collection software provided by PolymerChar. Chromatographic conditions can be set as follows: column oventemperature of 145° C.; flowrate of 1 mL/min; injection volume of 0.4mL; and polymer concentration of about 2 mg/mL, depending on samplemolecular weight. The temperatures for both the hot-transfer line andIRS detector sample cell are set at 150° C., while the temperature ofthe electronics of the IRS detector is set at 60° C. Short chainbranching content can be determined via an in-house method using theintensity ratio of CH₃ (I_(CH3)) to CH₂ (I_(CH2)) coupled with acalibration curve. The calibration curve is a plot of SCB content(x_(SCB)) as a function of the intensity ratio of I_(CH3)/I_(CH2). Toobtain a calibration curve, a group of polyethylene resins (no less than5) of SCB level ranging from zero to ca. 32 SCB/1,000 total carbons (SCBStandards) are used. All these SCB Standards have known SCB levels andflat SCBD profiles pre-determined separately by NMR and thesolvent-gradient fractionation coupled with NMR (SGF-NMR) methods. UsingSCB calibration curves thus established, profiles of short chainbranching distribution across the molecular weight distribution areobtained for resins fractionated by the IR5-GPC system under exactly thesame chromatographic conditions as for these SCB standards. Arelationship between the intensity ratio and the elution volume isconverted into SCB distribution as a function of MWD using apredetermined SCB calibration curve (i.e., intensity ratio of IcH3/IcH2vs. SCB content) and MW calibration curve (i.e., molecular weight vs.elution time) to convert the intensity ratio of IcH3/IcH2 and theelution time into SCB content and the molecular weight, respectively.

Although not tested, it is expected that the polymer blend compositionsdiscussed below do not have a decreasing comonomer distribution, i.e.,the polymer blend compositions have either a reverse short chainbranching distribution (increasing comonomer distribution) or a flatshort chain branching distribution (uniform comonomer distribution).

Dart impact strength (g/mil) was measured in accordance with ASTM D1709(method A). Film machine direction (MD) and transverse direction (TD)Elmendorf tear strengths (g/mil) were measured on a Testing Machinestear tester (Model 83-11-00) in accordance with ASTM D1922. SpencerImpact (J/mil) was determined in accordance with ASTM D3420. Film haze(%) was determined in accordance with ASTM D1003, and film clarity (%)was determined in accordance with ASTM 105.

Metals content, such as the amount of catalyst residue in the polymercomposition or film, was determined by ICP analysis on a PerkinElmerOptima 8300 instrument. Polymer samples were ashed in a Thermolynefurnace with sulfuric acid overnight, followed by acid digestion in aHotBlock with HC1 and HNO3 (3:1 v:v).

Differential Scanning calorimetry (DSC) was performed at a heating rateof 20 ° C./min, as described in ASTM D3418 (2nd heat, peak temperaturesin ° C.).

The long chain branches (LCB) per 1,000,000 total carbon atoms werecalculated using the method of Janzen and Colby (J. Mol. Struct.,485/486, 569-584 (1999)), from values of zero shear viscosity, η_(o)(determined from the Carreau-Yasuda model, described hereinabove), andmeasured values of Mw obtained using a Dawn EOS multiangle lightscattering detector (Wyatt). See also U.S. Pat. No. 8,114,946; J. Phys.Chem. 1980, 84, 649; and Y. Yu, D. C. Rohlfing, G. R Hawley, and P. J.DesLauriers, Polymer Preprints, 44, 49-50 (2003). These references areincorporated herein by reference in their entirety.

Examples 1-19

Low density polymer components (ethylene/1-hexene copolymers) were meltblended with high density polymer components (ethylene/1-hexenecopolymers or ethylene homopolymers) to produce Blend Examples B1-B19.The properties of the respective low density polymer components (LD 1 toLD 3) and high density polymer components (HD 1 to HD 4) are summarizedin Table I. These polymer components were produced using zirconium-basedmetallocene catalyst systems (homogeneously-branched polymercomponents). The polymer properties of LD 2 were very similar to LD 3,with the exception of the slightly higher melt index and lower density.The relative amounts of the low and high density components used inBlend Examples B1-B19 are summarized in Table II, and the properties ofthe blend compositions are summarized in Table III.

The blend compositions were produced using a ZSK-40 twin screw extruderwith a 30″ screw length. The heating and screw speed were adjusted toobtain a melt temperature of 275° C. for the polymer strand (Zone 1=250°C., Zone 2=245° C., Zone 3=245° C., Zone 4=230° C., Screw RPM=75). Thepolymer strand was cooled in a water bath, pelletized, and then dried toform the polymer compositions of Blend Examples B1-B19.

As shown in Table III, Blend Examples B1-B19 had densities in0.914-0.926 g/cm³ range, ratios of Mw/Mn in the 2-3 range, melt indicesin the 0.5-1.1 g/10 min range, and CY-a parameters (at 190° C.) in the0.4-0.6 range.

FIG. 1 illustrates the ATREF profiles of the ethylene polymercompositions of Blend Examples B1-B3, FIG. 2 illustrates the ATREFprofiles of the ethylene polymer compositions of Blend Examples B4-B6,FIG. 3 illustrates the ATREF profiles of the ethylene polymercompositions of Blend Examples B7-B9, and FIG. 4 illustrates the ATREFprofiles of the ethylene polymer compositions of Blend Examples B10-B14.These ATREF profiles are representative of the other ethylene polymercompositions of this invention, such as Blend Examples B15-B19. TheseATREF curves generally contain two peaks in the 60-104° C. range, withthe first peak (lower temperature peak) generally at a temperature inthe 60-72° C. range, and with the second peak (higher temperature peak)generally at a temperature in the 92-104° C. range. The respective peaktemperatures for Examples B1-B14 are summarized in Table IV. Thedifference between the temperatures of the two peaks (ΔT) was in the26-39° C. range. Note that the shoulders to the right of the 99.5-100.5°C. peaks in FIG. 1 are not considered to be peaks.

Blown film samples at a 1-mil thickness (25 microns) were produced fromBlend Examples B1-B19, low density components LD 1 and LD 3, and highdensity components HD 2 to HD 4. The blown film samples were made on alaboratory-scale blown film line using typical linear low densitypolyethylene conditions (LLDPE) as follows: 100 mm die diameter, 1.5 mmdie gap, 37.5 mm diameter single-screw extruder fitted with a barrierscrew with a Maddock mixing section at the end (L/D=24, 2.2:1compression ratio), 27 kg/hr output rate, 2.5:1 blow-up ratio (BUR),“in-pocket” bubble with a “frost line height” (FLH) of about 28 cm, and190° C. barrel and die set temperatures. Cooling was accomplished with aDual Lip air ring using ambient (laboratory) air at about 25° C. Theseparticular processing conditions were chosen because the blown filmproperties so obtained are typically representative of those obtainedfrom larger, commercial scale film blowing conditions.

Table I and Table III summarize the dart impact, Spencer impact, MD andTD Elmendorf tear strength, ratio of MD:TD tear strength, and opticalproperties of the blown film samples. Unexpectedly, the addition of thehigh density component to the low density component resulted in anincrease in the MD Elmendorf tear strength in all instances where over8% of the high density component was used. The amount of the MDElmendorf tear strength increase is shown in Table III, whichdemonstrates increases of over 100%. The MD:TD tear strength ratios forBlend Examples B1-B19 were in the 0.2-0.6 range, and much higher thanwould be expected given the very low MD:TD ratios for the high densitycomponents (0.05 to 0.22; see Table I). Also beneficially, the additionof the high density component to the low densitycomponent—unexpectedly—did not significantly decrease the dart impact,spencer impact, film haze, or film clarity. Blend Examples B1-B19retained excellent impact strength and optical properties, but with anincrease in MD Elmendorf tear strength.

The unexpected and beneficial balance of MD Elmendorf tear strength anddart impact strength is illustrated in FIGS. 5-7. FIG. 5 is a plot ofthe MD Elmendorf tear strength of blown films versus the amount of thehigh density component (wt. %) in the ethylene polymer composition,while FIG. 6 is a plot of the dart impact strength of blown films versusthe amount of the high density component (wt. %) in the ethylene polymercomposition, and FIG. 7 is a plot of the dart impact strength and thepercentage increase in MD Elmendorf tear strength of blown films versusthe amount of the high density component (wt. %) in the ethylene polymercomposition. These figures show a clear increase in the MD Elmendorftear strength as the amount of the high density component is increased.Dart impact, however, is not significantly affected by the high densitycomponent up to addition levels of approximately 20-25%, but after about30-35% of the high density component addition, the dart impact strengthis reduced. Thus, a good balance of tear resistance and impactproperties was found in the 15-35 wt. % range (e.g., 20-30 wt. % range)of high density addition. For end-use applications where dart impactstrength is more important, a range of ˜15-25 wt. % high density may bemore suitable, whereas for end-use applications where tear resistance ismore important, a range of ˜25-35 wt. % high density may be moresuitable.

Representative blown film samples of Blend Examples B11 and B13 wereanalyzed for residual metals, and the zirconium content was in the0.9-1.1 ppm range (by weight). The titanium content and hafnium contentwere less than 0.05 ppm, which was below the level of detection (nomeasurable amount).

FIG. 8 illustrates the second heat DSC curve for high density componentHD 3, which has only a single peak (and is representative of the otherhigh density components of this invention).

FIG. 9 presents an “Arnett plot,” wherein the log of the zero-shearviscosity is plotted against the log of the weight-average molecularweight, for Blend Examples B1-B6 and B10-B14, and is representative ofthe ethylene polymer compositions of this invention. When each point iscompared to the Janzen-Colby grid lines, the average number of longchain branches (LCB) in the polymer can be determined (Alpha is theaverage number of LCB per carbon atom). FIG. 9 shows the unexpectedlylow levels of LCB of the polymer compositions of this invention, withless than 10 LCB per 1,000,000 total carbon atoms, and in some cases,less than 1-3 LCB per 1,000,000 total carbon atoms.

Thus, the polymer compositions disclosed herein offer a beneficialcombination of density, molecular weight, melt flow, and ATREFproperties, resulting in film products with excellent impact resistanceand optical properties, but with improved tear resistance, particularlyin the machine direction, as quantified by the MD Elmendorf tearstrength.

TABLE I Polymer Density MI HLMI η₀ Component (g/cc) (g/10 min) (g/10min) HLMI/MI (Pa.s) CY-a Low Density Components LD 1 0.9114 1.02 18.717.8 8.350 0.484 LD 2 0.9106 0.75 — — — — LD 3 0.9119 0.61 12.1 19.813.270 0.456 High Density Components HD 1 0.9590 1.01 17.7 17.6 8.3600.519 HD 2 0.9517 1.14 18.3 16.2 7.020 0.609 HD 3 0.9423 1.08 17.2 17.77.350 0.604 HD 4 0.9545 0.53 11.5 19.9 13.690 0.564 Polymer Mn Mw Mz MpComponent (kg/mol) (kg/mol) (kg/mol) (kg/mol) Mw/Mn Mz/Mw Low DensityComponents LD 1 49 132 242 110 2.71 1.83 LD 2 — — — — — — LD 3 62 141247 117 2.26 1.76 High Density Components HD 1 47 140 281 110 2.98 2.01HD 2 45 141 263 116 3.15 1.86 HD 3 58 138 246 115 2.38 1.79 HD 4 47 156293 129 3.31 1.88 Dart Spencer Polymer Impact Impact MD Tear TD TearRatio of Haze Clarity Component (g/mil) (J/mil) (g/mil) (g/mil) MD/TD(%) (%) Low Density Components LD 1 1418 1.19 155 324 0.48 4.6 86 LD 2 —— — — — — — LD 3 1418 — 118 377 0.31 4.6 86 High Density Components HD 1— — — — — — — HD 2 23 0.27  39 177 0.22 20.8 — HD 3 48 0.28  30 219 0.1411.1 — HD 4 23 0.27  18 328 0.05 14.8 —

TABLE II Blend Low Density High Density Ratio of Example ComponentComponent LD/HD B1 LD 1 HD 1 91/9  B2 LD 1 HD 1 80/20 B3 LD 1 HD 1 70/30B4 LD 1 HD 2 90/10 B5 LD 1 HD 2 77/23 B6 LD 1 HD 2 64/36 B7 LD 1 HD 387/13 B8 LD 1 HD 3 70/30 B9 LD 1 HD 3 54/46 B10 LD 2 HD 1 81/19 B11 LD 2HD 2 90/10 B12 LD 2 HD 2 77/23 B13 LD 2 HD 2 65/35 B14 LD 2 HD 3 70/30B15 LD 3 HD 4 92/8  B16 LD 3 HD 4 80/20 B17 LD 3 HD 4 68/32 B18 LD 1 HD4 90/10 B19 LD 1 HD 4 78/22

TABLE III Blend Density MI HLMI η₀ Example (g/cc) (g/10 min) (g/10 min)HLMI/MI (Pa.s) CY-a B1  0.9155 1.02 18.9 18.6 7.620 0.453 B2  0.92011.05 18.4 17.5 8.460 0.487 B3  0.9254 1.05 18.5 17.6 6.350 0.433 B4 0.9153 1.09 18.6 17.1 8.370 0.492 B5  0.9202 1.08 18.7 17.3 7.920 0.523B6  0.9257 1.06 18.6 17.5 8.230 0.502 B7  0.9158 1.04 18.1 17.4 8.2100.497 B8  0.9210 1.05 18.5 17.6 7.970 0.516 B9  0.9260 1.06 17.9 16.97.890 0.536 B10 0.9207 0.72 13.4 18.6 10.550 0.483 B11 0.9159 0.71 12.918.1 10.960 0.479 B12 0.9212 0.77 13.5 17.5 9.890 0.497 B13 0.9252 0.7914.0 17.8 9.280 0.513 B14 0.9208 0.77 13.2 17.2 9.770 0.503 B15 0.91490.56 10.8 19.2 16.190 0.431 B16 0.9196 0.56 10.6 18.9 15.380 0.454 B170.9239 0.56 10.6 19.0 15.140 0.468 B18 0.9152 0.97 17.9 18.5 8.870 0.490B19 0.9202 0.97 16.4 16.9 9.460 0.497 Blend Mn Mw Mz Mp Example (kg/mol)(kg/mol) (kg/mol) (kg/mol) Mw/Mn Mz/Mw B1  47 130 236 113 2.78 1.81 B2 46 132 245 107 2.89 1.85 B3  47 135 250 122 2.87 1.86 B4  47 132 240 1162.78 1.82 B5  47 134 246 110 2.86 1.83 B6  46 132 241 113 2.84 1.82 B7 49 133 240 109 2.72 1.80 B8  47 133 241 116 2.81 1.81 B9  50 135 242 1212.71 1.80 B10 52 146 265 126 2.80 1.82 B11 53 146 262 124 2.72 1.80 B1254 145 260 127 2.70 1.80 B13 50 144 262 122 2.86 1.82 B14 52 144 256 1212.75 1.78 B15 65 147 265 123 2.28 1.80 B16 66 149 267 123 2.24 1.79 B1764 150 270 121 2.34 1.80 B18 58 130 232 107 2.26 1.78 B19 60 135 243 1102.26 1.80 Dart Spencer MD HD Blend Impact Impact MD Tear TD Tear Ratioof Tear Haze Clarity Component Example (g/mil) (J/mil) (g/mil) (g/mil)MD/TD Increase (%) (%) (wt. %) B1  1425 1.40 203 466 0.44  31% 7.3 85.29 B2  1418 0.16 232 547 0.42  49% 2.9 84.7 20 B3  288 0.38 243 676 0.36 57% 8.1 83.9 30 B4  1418 1.26 184 443 0.42  19% 6.0 85.6 10 B5  11730.69 268 588 0.46  73% 2.4 85.4 23 B6  283 0.31 287 618 0.46  85% 8.885.5 36 B7  1418 1.43 192 433 0.44  24% 4.5 85.7 13 B8  785 0.53 265 5480.48  71% 7.0 85.0 30 B9  173 0.27 301 586 0.51  94% 6.2 85.5 46 B101403 1.11 231 588 0.39  95% 5.0 84.3 19 B11 1418 1.59 167 498 0.33  41%3.0 85.9 10 B12 946 1.00 200 704 0.28  69% 4.7 86.0 23 B13 245 0.35 323603 0.54 174% 6.1 85.5 35 B14 318 0.83 202 596 0.34  71% 5.3 81.7 30 B151403 1.40 118 437 0.27  0% 4.7 85.8 8 B16 1418 0.90 154 551 0.28  30%6.8 85.6 20 B17 839 0.48 152 609 0.25  29% 8.7 85.7 32 B18 1418 1.35 205497 0.41  32% 5.2 85.7 10 B19 1418 0.70 257 602 0.43  66% 6.3 85.7 22

TABLE IV Low High Blend Temperature Temperature ΔT Example Peak (° C.)Peak (° C.) (° C.) B1 66.0 99.5 33.5 B2 66.4 99.6 33.2 B3 65.0 100.235.2 B4 65.7 97.9 32.2 B5 66.2 99.3 33.1 B6 67.8 98.1 30.3 B7 66.0 95.829.8 B8 65.2 97.1 31.9 B9 65.2 97.2 32.0 B10 64.4 98.6 34.2 B11 65.296.9 31.7 B12 64.9 98.3 33.4 B13 65.0 98.2 33.2 B14 64.5 97.0 32.5

The invention is described above with reference to numerous aspects andspecific examples. Many variations will suggest themselves to thoseskilled in the art in light of the above detailed description. All suchobvious variations are within the full intended scope of the appendedclaims. Other aspects of the invention can include, but are not limitedto, the following (aspects are described as “comprising” but,alternatively, can “consist essentially of” or “consist of”):

Aspect 1. An ethylene polymer composition comprising:

(i) a homogeneously-branched first ethylene polymer component; and

(ii) a homogeneously-branched second ethylene polymer component ofhigher density than the first ethylene polymer component;

wherein the amount of the second ethylene polymer component is in arange from about 15 to about 35 wt. %, based on the total weight of thefirst ethylene polymer component and the second ethylene polymercomponent; and

wherein the composition is characterized by:

-   -   a density in a range from about 0.912 to about 0.925 g/cm³;    -   a ratio of Mw/Mn in a range from about 2 to about 5;    -   a melt index less than or equal to about 2 g/10 min;    -   a CY-a parameter in a range from about 0.35 to about 0.7; and    -   an ATREF curve containing at least two peaks, with a first peak        at a temperature in a range from about 60 to about 72° C., and a        second peak at a temperature in a range from about 92 to about        104° C.

Aspect 2. The composition defined in aspect 1, wherein the compositionhas a density in any range disclosed herein, e.g., from about 0.912 toabout 0.922 g/cm³, from about 0.912 to about 0.92 g/cm³, from about0.915 to about 0.925 g/cm³, etc.

Aspect 3. The composition defined in aspect 1 or 2, wherein the firstethylene polymer component has a density in any range disclosed herein,e.g., from about 0.89 to about 0.92 g/cm³, from about 0.90 to about 0.92g/cm³, from about 0.905 to about 0.918 g/cm³, from about 0.91 to about0.918 g/cm³, etc.

Aspect 4. The composition defined in any one of aspects 1-3, wherein thesecond ethylene polymer component has a density in any range disclosedherein, e.g., from about 0.935 to about 0.972 g/cm³, from about 0.94 toabout 0.97 g/cm³, from about 0.94 to about 0.96 g/cm³, from about 0.945to about 0.965 g/cm³, etc.

Aspect 5. The composition defined in any one of aspects 1-4, wherein theamount of the second ethylene polymer component is in any rangedisclosed herein, e.g., from about 15 to about 30 wt. %, from about 15to about 25 wt. %, from about 20 to about 35 wt. %, from about 20 toabout 30 wt. %, from about 18 to about 32 wt. %, etc., based on thetotal weight of the first ethylene polymer component and the secondethylene polymer component.

Aspect 6. The composition defined in any one of aspects 1-5, wherein thecomposition and the first ethylene polymer component, independently,have a melt index (MI) in any range disclosed herein, e.g., less than orequal to about 2 g/10 min, less than or equal to about 1.5 g/10 min,from about 0.3 to about 2 g/10 min, from about 0.5 to about 1.8 g/10min, from about 0.5 to about 1.5 g/10 min, etc.

Aspect 7. The composition defined in any one of aspects 1-6, wherein thesecond ethylene polymer component has a melt index (MI) in any rangedisclosed herein, e.g., less than or equal to about 50 g/10 min, lessthan or equal to about 10 g/10 min, less than or equal to about 5 g/10min, from about 0.3 to about 2 g/10 min, from about 0.5 to about 8 g/10min, from about 0.4 to about 4 g/10 min, etc.

Aspect 8. The composition defined in any one of aspects 1-7, wherein thecomposition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a CY-a parameter in anyrange disclosed herein, e.g., from about 0.35 to about 0.7, from about0.35 to about 0.6, from about 0.4 to about 0.7, from about 0.4 to about0.65, from about 0.4 to about 0.55, from about 0.45 to about 0.7, fromabout 0.45 to about 0.65, etc.

Aspect 9. The composition defined in any one of aspects 1-8, wherein thecomposition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a reverse short chainbranching distribution (increasing comonomer distribution), e.g., thenumber of SCB per 1000 total carbon atoms of the polymer at Mw isgreater than at Mn, and/or the number of SCB per 1000 total carbon atomsof the polymer at Mz is greater than at Mw, and/or the number of SCB per1000 total carbon atoms of the polymer at Mz is greater than at Mn.

Aspect 10. The composition defined in any one of aspects 1-8, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a flat short chainbranching distribution (uniform comonomer distribution), e.g., a slopeof a plot of the number of short chain branches per 1000 total carbonatoms versus the logarithm of molecular weight of the olefin polymer(determined via linear regression over the range from D15 to D85) is ina range from about -0.6 to about 0.6, and/or a percentage of data pointsdeviating from the average short chain branch content by greater than0.5 short chain branches per 1000 total carbon atoms (determined overthe range from D15 to D85) is less than or equal to about 20%, and/or apercentage of data points deviating from the average short chain branchcontent by greater than 1 short chain branch per 1000 total carbon atoms(determined over the range from D15 to D85) is less than or equal toabout 10%.

Aspect 11. The composition defined in any one of aspects 1-10, whereinthe first ethylene polymer component and the second ethylene polymercomponent, independently, are produced using a zirconium-basedmetallocene catalyst system.

Aspect 12. The composition defined in any one of aspects 1-11, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of HLMI/MI inany range disclosed herein, e.g., from about 10 to about 35, from about12 to about 30, from about 12 to about 25, from about 12 to about 20,from about 15 to about 35, from about 15 to about 30, from about 15 toabout 25, from about 15 to about 22, etc.

Aspect 13. The composition defined in any one of aspects 1-12, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of Mw/Mn in anyrange disclosed herein, e.g., from about 2 to about 5, from about 2 toabout 4, from about 2 to about 3.5, from about 2 to about 3, from about2.2 to about 5, from about 2.2 to about 4, from about 2.2 to about 3.2,etc.

Aspect 14. The composition defined in any one of aspects 1-13, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a ratio of Mz/Mw in anyrange disclosed herein, e.g., from about 1.7 to about 3, from about 1.7to about 2.5, from about 1.7 to about 2.3, from about 1.7 to about 2.2,from about 1.7 to about 2, etc.

Aspect 15. The composition defined in any one of aspects 1-14, whereinthe composition and the first ethylene polymer component, independently,have a Mw in any range disclosed herein, e.g., from about 100 to about200 kg/mol, from about 100 to about 150 kg/mol, from about 110 to about200 kg/mol, from about 110 to about 180 kg/mol, from about 110 to about160 kg/mol, etc.

Aspect 16. The composition defined in any one of aspects 1-15, whereinthe second ethylene polymer component has a Mw in any range disclosedherein, e.g., from about 85 to about 200 kg/mol, from about 85 to about160 kg/mol, from about 100 to about 200 kg/mol, from about 40 to about180 kg/mol, from about 40 to about 150 kg/mol, etc.

Aspect 17. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 1.1:1 to about 5:1, from about 1.1:1 to about 3:1, fromabout 1.1:1 to about 1.8:1, from about 1.2:1 to about 4:1, from about1.2:1 to about 2.5:1, etc.

Aspect 18. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 0.5:1 to about 0.9:1, from about 0.6:1 to about 0.9:1,from about 0.65:1 to about 0.9:1, from about 0.7:1 to about 0.9:1, etc.

Aspect 19. The composition defined in any one of aspects 1-16, wherein aratio of the Mw of the first ethylene polymer component to the Mw of thesecond ethylene polymer component is in any range disclosed herein,e.g., from about 0.75:1 to about 1.25:1, from about 0.8:1 to about1.2:1, from about 0.9:1 to about 1.1:1, from about 0.8:1 to about 1.1:1,etc.

Aspect 20. The composition defined in any one of aspects 1-19, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, have a unimodal molecularweight distribution.

Aspect 21. The composition defined in any one of aspects 1-20, whereinthe composition and the first ethylene polymer component, independently,have a zero-shear viscosity in any range disclosed herein, e.g., fromabout 2,500 to about 25,000 Pa-sec, from about 3,000 to about 25,000Pa-sec, from about 2,500 to about 20,000 Pa-sec, from about 3,000 toabout 20,000 Pa-sec, etc.

Aspect 22. The composition defined in any one of aspects 1-21, whereinthe second ethylene polymer component has a zero-shear viscosity in anyrange disclosed herein, e.g., from about 2,500 to about 25,000 Pa-sec,from about 5,000 to about 70,000 Pa-sec, from about 150 to about 2,500Pa-sec, from about 500 to about 5,000 Pa-sec, etc.

Aspect 23. The composition defined in any one of aspects 1-22, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, contain no measurable amountof hafnium or titanium.

Aspect 24. The composition defined in any one of aspects 1-23, whereinthe first ethylene polymer component and the second ethylene polymercomponent, independently, are not produced using a hafnium-based and/ortitanium-based catalyst system.

Aspect 25. The composition defined in any one of aspects 1-24, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, contain less than 10 longchain branches (LCB), less than 8 LCB, less than 5 LCB, less than 3 LCB,etc., per million total carbon atoms.

Aspect 26. The composition defined in any one of aspects 1-25, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks, with a first peak (lower temperature peak) at a temperaturein any range disclosed herein, e.g., from about 62 to about 70° C., fromabout 63 to about 69° C., from about 64 to about 68° C., etc.

Aspect 27. The composition defined in any one of aspects 1-26, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks, with a second peak (higher temperature peak) at a temperaturein any range disclosed herein, e.g., from about 93 to about 103° C.,from about 94 to about 102° C., from about 95 to about 101° C., etc.

Aspect 28. The composition defined in any one of aspects 1-27, whereinthe composition is characterized by an ATREF curve containing at leasttwo peaks in the temperature range from about 60 to about 104° C., andthe difference between the temperatures of the two peaks (ΔT) is in anyrange disclosed herein, e.g., from about 26 to about 39° C., from about28 to about 37° C., from about 29 to about 36° C., etc.

Aspect 29. The composition defined in any one of aspects 1-28, whereinthe composition is a single reactor product, e.g., not a post-reactorblend.

Aspect 30. The composition defined in any one of aspects 1-28, whereinthe composition is a post-reactor blend.

Aspect 31. The composition defined in any one of aspects 1-30, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylenehomopolymer and/or an ethylene/α-olefin copolymer.

Aspect 32. The composition defined in any one of aspects 1-31, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylenehomopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexenecopolymer, and/or an ethylene/1-octene copolymer.

Aspect 33. The composition defined in any one of aspects 1-32, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylene/1-butenecopolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octenecopolymer.

Aspect 34. The composition defined in any one of aspects 1-33, whereinthe composition, the first ethylene polymer component, and the secondethylene polymer component, independently, comprise an ethylene/1-hexenecopolymer.

Aspect 35. The composition defined in any one of aspects 1-34, whereinthe total amount of the first ethylene polymer component and the secondethylene polymer component in the composition is in any range disclosedherein, e.g., at least about 75 wt. %, at least about 85 wt. %, at leastabout 90 wt. %, at least about 95 wt. %, etc., based on the total weightof the composition.

Aspect 36. The composition defined in any one of aspects 1-35, whereinthe composition further comprises any additive disclosed herein, e.g.,an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a filler, a polymer processing aid, a UV additive,etc., or combinations thereof.

Aspect 37. An article of manufacture comprising (or produced from) thecomposition defined in any one of aspects 1-36.

Aspect 38. An article of manufacture comprising (or produced from) thecomposition defined in any one of aspects 1-36, wherein the article isan agricultural film, an automobile part, a bottle, a container forchemicals, a drum, a fiber or fabric, a food packaging film orcontainer, a food service article, a fuel tank, a geomembrane, ahousehold container, a liner, a molded product, a medical device ormaterial, an outdoor storage product, outdoor play equipment, a pipe, asheet or tape, a toy, or a traffic barrier.

Aspect 39. A film comprising (or produced from) the polymer compositiondefined in any one of aspects 1-36.

Aspect 40. The film defined in aspect 39, wherein the film has a haze(with or without additives) in any range disclosed herein, e.g., lessthan or equal to about 12%, less than or equal to about 10%, from about2 to about 10%, from about 2 to about 8%, etc.

Aspect 41. The film defined in aspect 39 or 40, wherein the film has aclarity (with or without additives) in any range disclosed herein, e.g.,at least about 70%, at least about 75%, at least about 80%, at leastabout 85%, etc.

Aspect 42. The film defined in any one of aspects 39-41, wherein thefilm has a dart impact strength in any range disclosed herein, e.g.,greater than or equal to about 250 g/mil, greater than or equal to about500 g/mil, greater than or equal to about 700 g/mil, greater than orequal to about 1000 g/mil, etc.

Aspect 43. The film defined in any one of aspects 39-42, wherein thefilm has a Spencer impact strength in any range disclosed herein, e.g.,from about 0.3 to about 2 J/mil, from about 0.4 to about 1.5 J/mil, etc.

Aspect 44. The film defined in any one of aspects 39-43, wherein thefilm has a MD Elmendorf tear strength in any range disclosed herein,e.g., from about 100 to about 500 g/mil, from about 100 to about 450g/mil, from about 125 to about 425 g/mil, from about 150 to about 450g/mil, from about 200 to about 450 g/mil, etc.

Aspect 45. The film defined in any one of aspects 39-44, wherein thefilm has a TD Elmendorf tear strength in any range disclosed herein,e.g., from about 200 to about 800 g/mil, from about 300 to about 800g/mil, from about 400 to about 800 g/mil, etc.

Aspect 46. The film defined in any one of aspects 39-45, wherein thefilm has a ratio of MD Elmendorf tear strength to TD Elmendorf tearstrength (MD:TD) in any range disclosed herein, e.g., from about 0.25:1to about 0.8:1, from about 0.25:1 to about 0.6:1, from about 0.3:1 toabout 0.8:1, from about 0.3:1 to about 0.7:1, from about 0.3:1 to about0.6:1, etc.

Aspect 47. The film defined in any one of aspects 39-46, wherein thefilm has an average thickness in any range disclosed herein, e.g., fromabout 0.4 to about 20 mils, from about 0.5 to about 8 mils, from about0.8 to about 5 mils, from about 0.7 to about 2 mils, from about 0.7 toabout 1.5 mils, etc.

Aspect 48. The film defined in any one of aspects 39-47, wherein thefilm is a blown film.

Aspect 49. The film defined in any one of aspects 39-47, wherein thefilm is a cast film.

Aspect 50. A process for improving film tear strength of ahomogeneously-branched first ethylene polymer having a density in arange from about 0.90 to about 0.92 g/cm³, the process comprising:

(a) combining the first ethylene polymer with about 15 to about 35 wt. %of a homogeneously-branched second ethylene polymer having a density ina range from about 0.935 to about 0.972 g/cm³ to form an ethylenepolymer composition,

the composition characterized by a melt index of less than or equal toabout 2 g/10 min and a Mw from about 100 to about 200 kg/mol; and

(b) melt processing the composition through a film die to form a film;

wherein the addition of the second ethylene polymer increases a MDElmendorf tear strength of the film.

Aspect 51. A process for producing a film with a target MD Elmendorftear strength, the process comprising:

(a) combining a homogeneously-branched first ethylene polymer having adensity in a range from about 0.90 to about 0.92 g/cm³ with about 15 toabout 35 wt. % of a homogeneously-branched second ethylene polymerhaving a density in a range from about 0.935 to about 0.972 g/cm³ toform an ethylene polymer composition,

the composition characterized by a melt index of less than or equal toabout 2 g/10 min and a Mw from about 100 to about 200 kg/mol; and

(b) adjusting an amount of the second ethylene polymer in thecomposition, and melt processing the composition through a film die toproduce the film with the target MD Elmendorf tear strength;

wherein the tear strength increases as the amount of the second ethylenepolymer in the composition increases.

Aspect 52. The process defined in aspect 50 or 51, wherein thecomposition has a density in any range disclosed herein, e.g., fromabout 0.912 to about 0.922 g/cm³, from about 0.912 to about 0.92 g/cm³,from about 0.915 to about 0.925 g/cm³, etc.

Aspect 53. The process defined in any one of aspects 50-52, wherein thefirst ethylene polymer has a density in any range disclosed herein,e.g., from about 0.905 to about 0.92 g/cm³, from about 0.905 to about0.915 g/cm³, from about 0.90 to about 0.915 g/cm³, etc.

Aspect 54. The process defined in any one of aspects 50-53, wherein thesecond ethylene polymer has a density in any range disclosed herein,e.g., from about 0.94 to about 0.97 g/cm³, from about 0.94 to about 0.96g/cm³, from about 0.945 to about 0.965 g/cm³, from about 0.945 to about0.96 g/cm³, etc.

Aspect 55. The process defined in any one of aspects 50-54, wherein theamount of the second ethylene polymer is in any range disclosed herein,e.g., from about 15 to about 30 wt. %, from about 15 to about 25 wt. %,from about 20 to about 35 wt. %, from about 22 to about 35 wt. %, fromabout 20 to about 30 wt. %, from about 18 to about 32 wt. %, etc., basedon the total weight of the first ethylene polymer and the secondethylene polymer.

Aspect 56. The process defined in any one of aspects 50-55, wherein thecomposition and the first ethylene polymer, independently, have a meltindex (MI) in any range disclosed herein, e.g., less than or equal toabout 2 g/10 min, less than or equal to about 1.5 g/10 min, from about0.3 to about 2 g/10 min, from about 0.5 to about 1.8 g/10 min, fromabout 0.5 to about 1.5 g/10 min, etc.

Aspect 57. The process defined in any one of aspects 50-56, wherein thesecond ethylene polymer has a melt index (MI) in any range disclosedherein, e.g., less than or equal to about 50 g/10 min, less than orequal to about 10 g/10 min, less than or equal to about 5 g/10 min, fromabout 0.3 to about 2 g/10 min, from about 0.5 to about 8 g/10 min, fromabout 0.4 to about 4 g/10 min, etc.

Aspect 58. The process defined in any one of aspects 50-57, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a CY-a parameter in any range disclosedherein, e.g., from about 0.35 to about 0.7, from about 0.35 to about0.6, from about 0.4 to about 0.7, from about 0.4 to about 0.65, fromabout 0.4 to about 0.55, from about 0.45 to about 0.7, from about 0.45to about 0.65, etc.

Aspect 59. The process defined in any one of aspects 50-58, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a reverse short chain branchingdistribution (increasing comonomer distribution), e.g., the number ofSCB per 1000 total carbon atoms of the polymer at Mw is greater than atMn, and/or the number of SCB per 1000 total carbon atoms of the polymerat Mz is greater than at Mw, and/or the number of SCB per 1000 totalcarbon atoms of the polymer at Mz is greater than at Mn.

Aspect 60. The process defined in any one of aspects 50-58, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a flat short chain branching distribution(uniform comonomer distribution), e.g., a slope of a plot of the numberof short chain branches per 1000 total carbon atoms versus the logarithmof molecular weight of the olefin polymer (determined via linearregression over the range from D15 to D85) is in a range from about −0.6to about 0.6, and/or a percentage of data points deviating from theaverage short chain branch content by greater than 0.5 short chainbranches per 1000 total carbon atoms (determined over the range from D15to D85) is less than or equal to about 20%, and/or a percentage of datapoints deviating from the average short chain branch content by greaterthan 1 short chain branch per 1000 total carbon atoms (determined overthe range from D15 to D85) is less than or equal to about 10%.

Aspect 61. The process defined in any one of aspects 50-60, wherein thefirst ethylene polymer and the second ethylene polymer, independently,are produced using a zirconium-based metallocene catalyst system.

Aspect 62. The process defined in any one of aspects 50-61, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a ratio of HLMI/MI in any range disclosedherein, e.g., from about 10 to about 35, from about 12 to about 30, fromabout 12 to about 25, from about 12 to about 20, from about 15 to about35, from about 15 to about 30, from about 15 to about 25, from about 15to about 22, etc.

Aspect 63. The process defined in any one of aspects 50-62, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a ratio of Mw/Mn in any range disclosedherein, e.g., from about 2 to about 5, from about 2 to about 4, fromabout 2 to about 3.5, from about 2 to about 3, from about 2.2 to about5, from about 2.2 to about 4, from about 2.2 to about 3.2, etc.

Aspect 64. The process defined in any one of aspects 50-63, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a ratio of Mz/Mw in any range disclosedherein, e.g., from about 1.7 to about 3, from about 1.7 to about 2.5,from about 1.7 to about 2.3, from about 1.7 to about 2.2, from about 1.7to about 2, etc.

Aspect 65. The process defined in any one of aspects 50-64, wherein thecomposition and the first ethylene polymer, independently, have a Mw inany range disclosed herein, e.g., from about 100 to about 200 kg/mol,from about 100 to about 150 kg/mol, from about 110 to about 200 kg/mol,from about 110 to about 180 kg/mol, from about 110 to about 160 kg/mol,etc.

Aspect 66. The process defined in any one of aspects 50-65, wherein thesecond ethylene polymer has a Mw in any range disclosed herein, e.g.,from about 85 to about 200 kg/mol, from about 85 to about 160 kg/mol,from about 100 to about 200 kg/mol, from about 40 to about 180 kg/mol,from about 40 to about 150 kg/mol, etc.

Aspect 67. The process defined in any one of aspects 50-66, wherein aratio of the Mw of the first ethylene polymer to the Mw of the secondethylene polymer is in any range disclosed herein, e.g., from about1.1:1 to about 5:1, from about 1.1:1 to about 3:1, from about 1.1:1 toabout 1.8:1, from about 1.2:1 to about 4:1, from about 1.2:1 to about2.5:1, etc.

Aspect 68. The process defined in any one of aspects 50-66, wherein aratio of the Mw of the first ethylene polymer to the Mw of the secondethylene polymer is in any range disclosed herein, e.g., from about0.5:1 to about 0.9:1, from about 0.6:1 to about 0.9:1, from about 0.65:1to about 0.9:1, from about 0.7:1 to about 0.9:1, etc.

Aspect 69. The process defined in any one of aspects 50-66, wherein aratio of the Mw of the first ethylene polymer to the Mw of the secondethylene polymer is in any range disclosed herein, e.g., from about0.75:1 to about 1.25:1, from about 0.8:1 to about 1.2:1, from about0.9:1 to about 1.1:1, from about 0.8:1 to about 1.1:1, etc.

Aspect 70. The process defined in any one of aspects 50-69, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, have a unimodal molecular weight distribution.

Aspect 71. The process defined in any one of aspects 50-70, wherein thecomposition and the first ethylene polymer, independently, have azero-shear viscosity in any range disclosed herein, e.g., from about2,500 to about 25,000 Pa-sec, from about 3,000 to about 25,000 Pa-sec,from about 2,500 to about 20,000 Pa-sec, from about 3,000 to about20,000 Pa-sec, etc.

Aspect 72. The process defined in any one of aspects 50-71, wherein thesecond ethylene polymer has a zero-shear viscosity in any rangedisclosed herein, e.g., from about 2,500 to about 25,000 Pa-sec, fromabout 5,000 to about 70,000 Pa-sec, from about 150 to about 2,500Pa-sec, from about 500 to about 5,000 Pa-sec, etc.

Aspect 73. The process defined in any one of aspects 50-72, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, contain no measurable amount of hafnium ortitanium.

Aspect 74. The process defined in any one of aspects 50-73, wherein thefirst ethylene polymer and the second ethylene polymer, independently,are not produced using a hafnium-based and/or titanium-based catalystsystem.

Aspect 75. The process defined in any one of aspects 50-74, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, contain less than 10 long chain branches (LCB),less than 8 LCB, less than 5 LCB, less than 3 LCB, etc., per milliontotal carbon atoms.

Aspect 76. The process defined in any one of aspects 50-75, wherein thecomposition is characterized by an ATREF curve containing at least twopeaks, with a first peak (lower temperature peak) at a temperature inany range disclosed herein, e.g., from about 60 to about 72° C., fromabout 62 to about 70° C., from about 63 to about 69 ° C., from about 64to about 68° C., etc.

Aspect 77. The process defined in any one of aspects 50-76, wherein thecomposition is characterized by an ATREF curve containing at least twopeaks, with a second peak (higher temperature peak) at a temperature inany range disclosed herein, e.g., from about 92 to about 104° C., fromabout 93 to about 103° C., from about 94 to about 102° C., from about 95to about 101° C., etc.

Aspect 78. The process defined in any one of aspects 50-77, wherein thecomposition is characterized by an ATREF curve containing at least twopeaks in the temperature range from about 60 to about 104° C., and thedifference between the temperatures of the two peaks (ΔT) is in anyrange disclosed herein, e.g., from about 26 to about 39° C., from about28 to about 37° C., from about 29 to about 36° C., etc.

Aspect 79. The process defined in any one of aspects 50-78, wherein thecomposition is a single reactor product, e.g., not a post-reactor blend.

Aspect 80. The process defined in any one of aspects 50-78, wherein thecomposition is a post-reactor blend.

Aspect 81. The process defined in any one of aspects 50-80, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, comprise an ethylene homopolymer and/or anethylene/α-olefin copolymer.

Aspect 82. The process defined in any one of aspects 50-81, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, comprise an ethylene homopolymer, anethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or anethylene/1-octene copolymer.

Aspect 83. The process defined in any one of aspects 50-82, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, comprise an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.

Aspect 84. The process defined in any one of aspects 50-83, wherein thecomposition, the first ethylene polymer, and the second ethylenepolymer, independently, comprise an ethylene/1-hexene copolymer.

Aspect 85. The process defined in any one of aspects 50-84, wherein thetotal amount of the first ethylene polymer and the second ethylenepolymer in the composition is in any range disclosed herein, e.g., atleast about 75 wt. %, at least about 85 wt. %, at least about 90 wt. %,at least about 95 wt. %, etc., based on the total weight of thecomposition.

Aspect 86. The process defined in any one of aspects 50-85, wherein thecomposition further comprises any additive disclosed herein, e.g., anantioxidant, an acid scavenger, an antiblock additive, a slip additive,a colorant, a filler, a polymer processing aid, a UV additive, etc., orcombinations thereof.

Aspect 87. The process defined in any one of aspects 50-86, wherein thefilm has a haze (with or without additives) in any range disclosedherein, e.g., less than or equal to about 12%, less than or equal toabout 10%, from about 2 to about 10%, from about 2 to about 8%, etc.

Aspect 88. The process defined in any one of aspects 50-87, wherein thesecond ethylene polymer does not substantially change the haze of thefilm, i.e., the change in haze is within +/−3 (percent haze units).

Aspect 89. The process defined in any one of aspects 50-88, wherein thefilm has a clarity (with or without additives) in any range disclosedherein, e.g., at least about 70%, at least about 75%, at least about80%, at least about 85%, etc.

Aspect 90. The process defined in any one of aspects 50-89, wherein thefilm has a dart impact strength in any range disclosed herein, e.g.,greater than or equal to about 250 g/mil, greater than or equal to about500 g/mil, greater than or equal to about 700 g/mil, greater than orequal to about 1000 g/mil, etc.

Aspect 91. The process defined in any one of aspects 50-90, wherein thesecond ethylene polymer does not substantially change the dart impactstrength of the film, i.e., the change in dart impact is less than about20%.

Aspect 92. The process defined in any one of aspects 50-91, wherein thefilm has a Spencer impact strength in any range disclosed herein, e.g.,from about 0.3 to about 2 J/mil, from about 0.4 to about 1.5 J/mil, etc.

Aspect 93. The process defined in any one of aspects 50-92, wherein theMD Elmendorf tear strength is in any range disclosed herein, e.g., fromabout 100 to about 500 g/mil, from about 100 to about 450 g/mil, fromabout 125 to about 425 g/mil, from about 150 to about 450 g/mil, fromabout 200 to about 450 g/mil, etc.

Aspect 94. The process defined in any one of aspects 50-93, wherein thefilm has a TD Elmendorf tear strength in any range disclosed herein,e.g., from about 200 to about 800 g/mil, from about 300 to about 800g/mil, from about 400 to about 800 g/mil, etc.

Aspect 95. The process defined in any one of aspects 50-94, wherein thefilm has a ratio of MD Elmendorf tear strength to TD Elmendorf tearstrength (MD:TD) in any range disclosed herein, e.g., from about 0.25:1to about 0.8:1, from about 0.25:1 to about 0.6:1, from about 0.3:1 toabout 0.8:1, from about 0.3:1 to about 0.7:1, from about 0.3:1 to about0.6:1, etc.

Aspect 96. The process defined in any one of aspects 50-95, wherein thefilm has an average thickness in any range disclosed herein, e.g., fromabout 0.4 to about 20 mils, from about 0.5 to about 8 mils, from about0.8 to about 5 mils, from about 0.7 to about 2 mils, from about 0.7 toabout 1.5 mils, etc.

Aspect 97. The process defined in any one of aspects 50-96, wherein theis a blown film.

Aspect 98. The process defined in any one of aspects 50-96, wherein thefilm is a cast film.

1. A film comprising an ethylene polymer composition, the compositioncomprising: (i) a homogeneously-branched first ethylene polymercomponent; and (ii) a homogeneously-branched second ethylene polymercomponent of higher density than the first ethylene polymer component;wherein the amount of the second ethylene polymer component is in arange from about 15 to about 35 wt. %, based on the total weight of thefirst ethylene polymer component and the second ethylene polymercomponent; and wherein the composition is characterized by: a density ina range from about 0.912 to about 0.925 g/cm³; a ratio of Mw/Mn in arange from about 2 to about 5; a melt index less than or equal to about2 g/10 min; a CY-a parameter in a range from about 0.35 to about 0.7;and an ATREF curve containing at least two peaks, with a first peak at atemperature in a range from about 60 to about 72° C., and a second peakat a temperature in a range from about 92 to about 104° C.
 2. The filmof claim 1, wherein the film has: a ratio of MD Elmendorf tear strengthto TD Elmendorf tear strength (MD:TD) in a range from about 0.25:1 toabout 0.8:1; and a MD Elmendorf tear strength in a range from about 100to about 500 g/mil.
 3. The film of claim 1, wherein the film is a blownfilm having an average thickness in a range from about 0.5 to about 8mils.
 4. The film of claim 1, wherein the film has: a haze of less thanor equal to about 10%; and a dart impact strength of greater than orequal to about 250 g/mil.
 5. The film of claim 1, wherein the film has:a MD Elmendorf tear strength in a range from about 125 to about 425g/mil; and a TD Elmendorf tear strength in a range from about 200 toabout 800 g/mil.
 6. The film of claim 1, wherein: the composition has aMw in a range from about 100 to about 200 kg/mol; the compositioncomprises an ethylene homopolymer, an ethylene/α-olefin copolymer, or acombination thereof; and the composition contains no measurable amountof hafnium or titanium.
 7. The film of claim 1, wherein: the density isin a range from about 0.915 to about 0.925 g/cm³; the ratio of Mw/Mn isin a range from about 2 to about 3.5; the melt index is in a range fromabout 0.3 to about 2 g/10 min; and the CY-a parameter is in a range fromabout 0.4 to about 0.65.
 8. The film of claim 1, wherein the amount ofthe second ethylene polymer component is in a range from about 20 toabout 30 wt. %, based on the total weight of the first ethylene polymercomponent and the second ethylene polymer component.
 9. The film ofclaim 1, wherein a ratio of the Mw of the first ethylene polymercomponent to the Mw of the second ethylene polymer component is in arange from about 0.8:1 to about 1.2:1.
 10. The film of claim 1, whereina difference between the temperatures (ΔT) of the first peak and thesecond peak is in a range from about 26 to about 39° C.
 11. The film ofclaim 1, wherein the first peak is at a temperature in a range fromabout 63 to about 69° C., and the second peak is at a temperature in arange from about 94 to about 102° C.
 12. An ethylene polymer compositioncomprising: (i) a homogeneously-branched first ethylene polymercomponent; and (ii) a homogeneously-branched second ethylene polymercomponent of higher density than the first ethylene polymer component;wherein the amount of the second ethylene polymer component is in arange from about 15 to about 35 wt. %, based on the total weight of thefirst ethylene polymer component and the second ethylene polymercomponent; and wherein the composition is characterized by: a density ina range from about 0.912 to about 0.925 g/cm³; a ratio of Mw/Mn in arange from about 2 to about 5; a melt index less than or equal to about2 g/10 min; a CY-a parameter in a range from about 0.35 to about 0.7;and an ATREF curve containing at least two peaks, with a first peak at atemperature in a range from about 60 to about 72° C., and a second peakat a temperature in a range from about 92 to about 104° C.
 13. Thecomposition of claim 12, wherein the composition: has a Mw in a rangefrom about 100 to about 200 kg/mol; has a unimodal molecular weightdistribution; contains no measurable amount of hafnium or titanium; andcontains less than 10 long chain branches (LCB) per million total carbonatoms.
 14. The composition of claim 12, wherein: the compositioncomprises an ethylene homopolymer, an ethylene/α-olefin copolymer, or acombination thereof; the composition is a single reactor product; and adifference between the temperatures (ΔT) of the first peak and thesecond peak is in a range from about 26 to about 39° C.
 15. Thecomposition of claim 12, wherein: the composition comprises an ethylenehomopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexenecopolymer, an ethylene/1-octene copolymer, or any combination thereof;the composition is a post-reactor blend; and the first peak is at atemperature in a range from about 63 to about 69° C., and the secondpeak is at a temperature in a range from about 94 to about 102° C.16-20. (canceled)
 21. The composition of claim 12, wherein: the ratio ofMw/Mn is in a range from about 2 to about 3.5; the melt index is in arange from about 0.3 to about 2 g/10 min; the CY-a parameter is in arange from about 0.4 to about 0.65; and the composition comprises anethylene homopolymer, an ethylene/1-butene copolymer, anethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or anycombination thereof.
 22. The composition of claim 21, wherein the firstpeak is at a temperature in a range from about 63 to about 69° C., andthe second peak is at a temperature in a range from about 94 to about102° C.
 23. The composition of claim 21, wherein the compositioncontains: no measurable amount of hafnium or titanium; and less than 10long chain branches (LCB) per million total carbon atoms.
 24. Thecomposition of claim 21, wherein the composition has a Mw in a rangefrom about 100 to about 200 kg/mol.
 25. The composition of claim 21,wherein a difference between the temperatures (ΔT) of the first peak andthe second peak is in a range from about 26 to about 39° C.
 26. Thecomposition of claim 21, wherein the composition has: a ratio of HLMI/MIin a range from about 12 to about 25; and a ratio of Mz/Mw in a rangefrom about 1.7 to about 2.2.